Turning off capitalization after an em-dash?

I generally use em-dashes to set off a parenthetical in the middle of a sentence. I never, ever want a capital letter after an em-dash, unless it’s a word that starts with a capital letter.

Is there a way to turn this behavior off?

I’m assuming you are using the option that tries to capitalise words for you, but what mechanism are you using to type in an em-dash? The default system doesn’t trigger capitalisation after a dash substitution, which is why I ask. Are you using a third-party text substitution tool, perhaps?

I don’t think I’m using any third party tools of any sort.

I always use “–” to enter em-dashes.

What’s weirder now that I’ve tried to a few different things, is that this doesn’t happen every time. Just often enough to make me stop and have to force a lowercase letter in. I will see if I can come up with specific situations to make this happen.

I use…
Alt shift - (that’s a regular dash at the end)
…for an em dash. Don’t have the capitalisation issue.

Alt -
…gives an en dash.